1. Field
Embodiments described generally relate to methods for starting up a gasifier. More particularly, such embodiments relate to transitioning a gasifier from an initial or starting state to a steady or operating state.
2. Description of the Related Art
Gasification is a high-temperature process usually conducted at elevated pressure to convert carbon-containing materials into carbon monoxide and hydrogen gas. Since this gas is often used for the synthesis of chemicals or synthetic hydrocarbon fuels, the gas is often referred to as “synthesis gas” or “syngas.” Typical feeds to gasification processes include petroleum-based materials that are neat or residues of processing materials, such as heavy crude oil, coals, bitumen recovered from tar sands, kerogen from oil shale, coke, and other high-sulfur and/or high metal-containing residues; gases; and various carbonaceous waste materials. The feedstock materials can be reacted in the gasifier in a reducing (oxygen-starved) atmosphere at high temperature and (usually) high pressure. The resulting syngas typically contains about 85 percent of the feedstocks carbon content as carbon monoxide, with the balance being a mixture of carbon dioxide and methane.
To start the gasifier, a separate start-up heater is typically used to combust a start-up fuel to produce a combustion gas that is then directed to the gasifier to heat the gasifier to desired gasification temperatures. Such introduction of the combustion gas for start-up typically introduces undesired impurities or compounds, e.g., water, steam, oxygen, and/or carbon monoxide, which can cause problems within the gasifier and/or downstream components. For example, the water or steam can condense in downstream components such as a particulate control or particulate filter device that does not operate well when water is present.
There is a need, therefore, for improved systems and methods for transitioning a gasifier from an initial or start-up state to a steady or operating state.